The quest for precision is one of the driving forces for technical innovation in watchmaking. This precision is in great part determined by the performance of an oscillator, the oscillation frequency of which generates a time signal that determines the timebase exploited by the mechanism of a wristwatch for finally indicating the time on a display.
A first solution in the prior art consists of a mechanical oscillator, based on a flywheel, called a balance wheel, coupled to a spiral spring. The stability of a mechanical oscillator is of the order of one second per day, despite the efforts of innovation based on the choice of particular materials, as is described for example in the documents EP 0 886 195 and EP 1 422 436.
A second solution in the prior art consists of a quartz oscillator, which can achieve a precision of one second per month, or even one second per year using more complicated temperature-compensated devices in order to avoid any drift caused by temperature variations, as is described in document WO 2008/125646.
Finally, a third solution, which is relatively theoretical as it is tricky to carry out in practice, is envisioned in the documents EP 1 852 756 and EP 1 906 271 using an atomic oscillator, based on the known effect of coherent population trapping (CPT), which makes it possible to measure a light intensity transmitted through a mixture of atoms, such as cesium or rubidium atoms. In theory, this solution makes it possible to obtain an oscillator which is more precise than that of the first two solutions. However, these documents do not provide information about the specific construction of an atomic oscillator within a wristwatch. For example, the atomic oscillator is used intermittently without any explanation as to the specific stable implementation of such a principle. Nor is it specified how to achieve both consumption and volume compatible with implementation in a wristwatch.